Dynamic-agent-Jenkins

A small project to implement dynamic agents for Jenkins

Steps:

• First thing is to set up the dev cluster where we are going to try all the mess. u can also use your own cluster in place of this dev cluster

  • using Kind let's create the cluster kind create cluster --config cluster-config.yaml this will create the cluster.
  • We can check the details of the cluster using kubectl kubectl cluster-info --context kind-kind
  • To install reffer https://kind.sigs.k8s.io/.

• Now lets create a namespace in K8s which we are going to use

  • kubectl create namespace jenkins this will create the namespace named jenkins.
  • Make sure to keep a record of the namespace for future ref.

• We have to create a service account with admin privileges as we are going to use this service account to perform all the required actions on the cluser.

  • to create the service account just apply the serviceAccount.yaml file on the approprate context and namespace kubectl apply -f .\serviceAccount.yaml --context kind-kind -n jenkins

  • this file will create the following:

    1. ServiceAccount with the name jenkins in the jenkins namespace.
    2. Secret with the name jenkins-token in the jenkins namespace. This secret is of type kubernetes.io/service-account-token, and has an annotation kubernetes.io/service-account.name with the value jenkins, which is required for the token to be valid.
    3. ClusterRoleBinding with the name jenkins-cr. This binds the cluster-admin role to the jenkins service account in the jenkins namespace.

  • once the account is created successfully we can get the token for the jenkins service account using the following command kubectl get secret jenkins-token --namespace jenkins --context kind-kind -o jsonpath='{.data.token}' make sure to change the necessary information if u make any changes in the yaml file .

  • this will return a base64 encoded value so make sure to decode it before you use it.

• Installing the K8s plugin in Jenkins

  • instruction on how to install https://plugins.jenkins.io/kubernetes/

• Once we are done installing we can move on to config part of the plugin

  • go to Dashboard>Manage Jenkins>Manage nodes and clouds>Configure Clouds and add a new cloud and select Kubernetes.
  • config the required settings like
    • Name : kubernetes or whatever you want to set, just make sure u remember it as this is going to be the name of the agent on which the jobs can be executed.
    • Kubernetes URL : we can get the URL for this from cluster-info command
    • Disable https certificate check : in case you don’t have a valid https cert mark it True
    • Kubernetes Namespace : the namespace we created jenkins
    • Jenkins URL : Change it if u are using localhost or you cant route a named entry.
    • WebSocket : mark it True
    • Credentials : create a new secret text credential with the value of jenkins-token as the id .
  • now we can save it and the connection is ready to run jobs.
  • we can define pod template also in case we need it.

• Creating a job:

  • we can create jobs to run on k8s by setting the agent to kubernetes
  • example :

  pipeline {
    agent {
      kubernetes {
        yaml '''
          apiVersion: v1
          kind: Pod
          spec:
            containers:
            - name: alpine
              image: alpine
              tty: true
          '''
      }
    }
    stages {
      stage('test run') {
        steps {
          container('alpine') {
            sh 'echo "hello world" && sleep 120'
          }
        }
      }
    }
  }

  we first define the the pod where we want to run the job then we use the container using the container option with the name of the container as argument.